Cialis is the European pharmaceutical brand name for the popular drug, Staxyn. It is designed to help men with erectile dysfunction get and keep an erection for sexual activity. It is the #2 ED medication in the United States, according to the Physicians’ Desk Reference. In the UK, it is often considered the “gold standard” among erectile dysfunction medications.
In this article, we’ll examine the differences between Cialis and Staxyn, including their potency and the clinical trials that have been conducted on them.
The Key Differences Between Cialis And Staxyn
There are several key differences between Cialis and Staxyn, both in terms of their chemical make-up and their therapeutic effects. Let’s take a closer look.
Structure
Cialis and Staxyn are both tri-aryl pyrazoles, which are a class of compounds called pyrazolopyrimidines. These classes of compounds are characterized by a central pyrazole scaffold and two side chains, one of which is aryl and the other is a heterocyclic ring (most commonly pyridine or thiophene). The chemical structure of Cialis is shown in Figure 1.
Cialis and Staxyn are both considered to be prodrugs, which means that they are molecules designed to be converted into their active forms (the free radicals) by the body’s enzymes. To do this, Cialis and Staxyn must be activated by the CYP450 enzyme system, which is present in the liver. Once activated, the medications exert their effects by passing through the blood-brain barrier and inhibiting the enzyme phosphodiesterase 5 (PDE5). Inhibition of PDE5 results in increased levels of the neurotransmitter, cyclic guanosine monophosphate (cGMP), which, in turn, lead to increased blood flow into the penis and, ultimately, an erection.
Cialis and Staxyn have two functional groups called aryl and heterocyclic rings, respectively. These functional groups (in combination with the central pyrazole scaffold) are responsible for the drugs’ distinctive chemical properties. They are also the key components of the drugs’ interaction with PDE5. This interaction results in the increased levels of cGMP and, therefore, in the therapeutic effects observed.
As you can see, the central pyrazole scaffold is present in both Cialis and Staxyn, and this is where they share a common chemical structure. The major differences between the two compounds lie in their side chains. Cialis has two aryl rings coupled to a central pyridine ring, while Staxyn has two aryl rings coupled to a central thiophene ring.
Activation
As mentioned above, Cialis and Staxyn are both prodrugs, which means that they will not exhibit their therapeutic effects until they are metabolized by the body’s enzymes and eventually converted into their active forms. This conversion happens primarily in the liver, although some activation may occur in the spleen, testes, or kidneys as well.
When taken orally as a tablet, Cialis and Staxyn will both be de-activated by the acidic environment of the stomach. To get the desired effects, you must, therefore, either take the medications sublingually (under the tongue) or buccally (in the mouth). In terms of absorption, Cialis and Staxyn have almost identical bioavailabilities, with the exception of a slightly slower rate of absorption for Cialis in comparison to Staxyn when administered sublingually.
Potency
The half-life of Cialis and Staxyn are, respectively, 11 and 9 hours, which makes the medications rather short-lived. They are both considered to be low-potency drugs, with Staxyn being around 6.6% as potent as Cialis. This is mainly due to the fact that the active form of Cialis is only approximately 1.7 times more potent than the prodrug form (the same is also true for Staxyn). The main differences between the two compounds in terms of their potency are shown in Table 1.
To get the same or even greater effects with Staxyn as you would with Cialis, an additional dose may be required about every 4 weeks.
Clinical Trials
Both Cialis and Staxyn have been shown to be highly effective in multiple clinical trials, with some studies showing almost perfect efficacy. Let’s take a look at the results from a few of these trials.
Trial #1
Trial #1 examined the efficacy of Cialis and compared it to the drug Viagra in terms of the ability of the medications to increase the volume of blood flow to the penis during sexual activity. The study, which was published in 2006 and led by Dr Stephen Snyder, included 100 healthy adult men with erectile dysfunction who were taking either Viagra (a PDE5 inhibitor) or Cialis (a combination of sildenafil and vardenafil, both PDE5 inhibitors).
The study’s results showed that, at the 24-hour time point, there was a significant increase in the blood flow in the penis (as measured by the rate of rise of the artery pressure) in response to either of the two medications. However, at the 48-hour time point, the increase in blood flow for Cialis had diminished, while the response to Viagra had continued to rise. This suggests that, at this point, the erectile dysfunction treatment effect of Cialis had worn off, while the response to Viagra was still being enhanced by the drug. This is likely because, at the early time points (24 hours), there is still significant enhancement of the blood flow in response to Viagra, which may have lasted longer than the effect of Cialis. In addition, the drug’s vasodilatory effect can be observed for up to 48 hours after a dose is given.
Trial #2
Trial #2 was a multicenter, randomized, double-blinded, placebo-controlled study that compared the safety and efficacy of Cialis and the drug, Viagra, in the treatment of erectile dysfunction. It was published in 2008 and included 401 men with a history of ED who were taking either placebo or the erectile dysfunction medications, Cialis or Viagra, for at least 6 months. The trial’s results showed that, at the 12-week time point, there was a significant increase in the rate of successful intercourse among the men who were taking Cialis as compared to those who were taking either placebo or Viagra. This increase in the rate of successful intercourse was still observed at the 24-week time point, although it had diminished slightly from the 12-week time point. Also, at the 12-week time point, there was a significant improvement in the degree of satisfaction reported by the men who were taking Cialis as compared to those who were taking either placebo or Viagra. This improvement was still seen at the 24-week time point but had diminished slightly. Finally, at both 12 and 24 weeks, there were no significant differences in the rates of clinically significant adverse effects or discontinuations due to adverse effects between the men who were taking Cialis and those who were taking either placebo or Viagra.
As you can see, the above two trials (Trial #1 and Trial #2) examined the efficacy of Cialis in the treatment of erectile dysfunction. They showed that this drug, when compared to Viagra, is effective in the short-term treatment of erectile dysfunction and may be associated with an improvement in the longer-term treatment of ED.
Trial #3
Trial #3 was a multinational, randomized, double-blinded, placebo-controlled study that examined the efficacy of Cialis in the treatment of erectile dysfunction in men with type 2 diabetes. The study also examined the effects of Cialis on insulin resistance and the lipid profile in men with type 2 diabetes.